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Question About Commercial Spiders

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#1 NeilPerlin

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Posted 21 November 2017 - 11:22 AM

I recently finished a 10" that has a homemade arched-vane spider that I built out of an aluminum ruler and some scrap wood based on the article in Sky and Telescope. It was fun to do but it has a vibration that I can't get rid of so, sadly, I think it's time to go to a commercial spider.

 

I've been reading the discussions about spiders and see both good and bad things about the Astrosystems and ProtoStar spiders?  Any recommendations between the two of them, and any other vendors?



#2 bvillebob

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Posted 21 November 2017 - 11:24 AM

Do a search on here for Protostar, I think you'll find that you don't want to try to order there.   Apparently the web site it still taking orders but the shipping department isn't aware of that.


Edited by bvillebob, 21 November 2017 - 11:24 AM.

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#3 havasman

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Posted 21 November 2017 - 11:35 AM

I have Astrosystems spiders, secondary holders, secondaries and secondary dew control systems on all my Dobs and they work great. Randy knows his product and can be as helpful as you need. The product matches the prints on the website exactly, a relatively rare and very helpful thing when you're laying out an installation. Highly recommended.

 

As above, Protostar has mostly been vaporware for the last couple of years. Recommendation = run away.


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#4 jim kuhns

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Posted 21 November 2017 - 11:46 AM

Would you send a picture of the spider attached? There is a possibly some one on this site who is a scope builder might being able to help. As others above had said,  I would not send my hard earned money to Protostar if you do, kiss it good by.



#5 Ishtim

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Posted 21 November 2017 - 11:47 AM

+1 on AstroSystems spiders. I just installed one holding a 2.38" secondary for a 10" f/4.5. 



#6 Pinbout

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Posted 21 November 2017 - 12:04 PM

I recently finished a 10" that has a homemade arched-vane spider that I built out of an aluminum ruler and some scrap wood based on the article in Sky and Telescope. It was fun to do but it has a vibration that I can't get rid of so, sadly, I think it's time to go to a commercial spider.

 

I've been reading the discussions about spiders and see both good and bad things about the Astrosystems and ProtoStar spiders?  Any recommendations between the two of them, and any other vendors?

if you double arched it it may strengthen it.

 

stainless steel rulers are better.

 

even banding straps.

 

I like the wood hub cause its lighter than anything out there and if its hard maple you can tap it without using inserts. and you can use nylon screws that add compression to the system. commercial spiders don't.

 

med_gallery_106859_3508_274124.jpg


Edited by Pinbout, 21 November 2017 - 12:06 PM.


#7 NeilPerlin

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Posted 21 November 2017 - 04:55 PM

Would you send a picture of the spider attached? There is a possibly some one on this site who is a scope builder might being able to help. As others above had said,  I would not send my hard earned money to Protostar if you do, kiss it good by.

I just got on this forum today and can't quite figure out how to attach an image yet. Sorry...

 

However, my spider is exactly as defined by Gary Seronek in his S&T article. See http://garyseronik.c...-mirror-holder/ In fact, I used that exploded parts view when I built it.

The trouble seems to be at the point where the spider hub attaches to the vane. My guess is that because it's attached towards the rear of the hub, most of the weight, including the secondary mirror, is too far down the hub, making it unbalanced and very susceptible to my touching the tube or even wind.

 

I can see how it might be stabilized by adding a second vane on the opposite side and closer to the mirror, effectively turning it into a 4 vane spider, at which point, after dismantling, redoing, and re-attaching the spider, I might as well buy a commercial one. Any ideas how I could stabilized without completely re-doing it (in which case I might as well just buy a commercial spider).

 

Thanks for the ideas.



#8 NeilPerlin

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Posted 21 November 2017 - 04:59 PM

And thanks for the assessment of ProtoStar. The spiders look really good but I tried calling with no answer and no voice mail. So unless someone has a simple idea about fixing my curved vane spider, I'll probably just buy an AstroSystems unit. And thanks for the responses.



#9 Jon Isaacs

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Posted 21 November 2017 - 05:09 PM

And thanks for the assessment of ProtoStar. The spiders look really good but I tried calling with no answer and no voice mail. So unless someone has a simple idea about fixing my curved vane spider, I'll probably just buy an AstroSystems unit. And thanks for the responses.

 

I had a scope with a protostar secondary mount.  The center bolt was nylon..  I tightened the adjustment screws down thinking it was steel and snapped the bolt.  Fortunately,  the flying secondary did not damage the primary nor did it damage itself. 

 

Jon



#10 Pinbout

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Posted 21 November 2017 - 07:13 PM

 

I just got on this forum today and can't quite figure out how to attach an image yet. Sorry

 

https://youtu.be/SJWsqTOnF5o



#11 Pinbout

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Posted 21 November 2017 - 07:16 PM

 

The center bolt was nylon..  I tightened the adjustment screws down thinking it was steel and snapped the bolt.

Its specifically designed to be compliant. Otherwise he'd need a pivot bearing. Just the slop in a threaded hole with 60% thread contact isn't enough.



#12 Jon Isaacs

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Posted 21 November 2017 - 07:39 PM

 

 

The center bolt was nylon..  I tightened the adjustment screws down thinking it was steel and snapped the bolt.

Its specifically designed to be compliant. Otherwise he'd need a pivot bearing. Just the slop in a threaded hole with 60% thread contact isn't enough.

 

 

 

I understood the design once it popped off.  IMHO,  not a good design.  There are better ways to provide the needed rotation that are more robust.  Astrosystems uses steel bolts. 

 

Regardless of my opinion of the design, the purpose of my post was to alert potential purchasers of the fact that the center bolt is nylon and can fail. 

 

Jon



#13 Jeff Morgan

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Posted 21 November 2017 - 08:24 PM

If you can make a curved vane spider at home, consider making an offset spider, either with vanes or wire. They don't require high tube-deforming tension to maintain rigidity, a much better design overall.

 

There are a lot of good threads on this forum about wire spiders. My next project will feature one. It looks incredibly easy. More so than solid vanes actually.

 

I don't like to say "never" because "never" is a very long time indeed. But having tried offset I'll never go back to the conventional layout where the vanes meet at the center bolt. 

 

https://www.cloudyni...-spider-design/

https://www.cloudyni...le-light-cheap/


Edited by Jeff Morgan, 21 November 2017 - 08:27 PM.

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#14 NeilPerlin

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Posted 22 November 2017 - 06:46 AM

Would you send a picture of the spider attached? There is a possibly some one on this site who is a scope builder might being able to help. As others above had said,  I would not send my hard earned money to Protostar if you do, kiss it good by.

And here's the picture of the spider. (I missed one step when trying to attach the picture yesterday.)

 

Spider - Small.jpg

 

Like I said, I think the problem is that the hub is mounted toward the back, which puts most of the weight forward and makes the unit unbalanced.



#15 Pinbout

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Posted 22 November 2017 - 09:26 AM

its not wide enough, that's why its shakin'

 

you material choice should be fine if you remake it like below...

 

just shorten the screws after you get it worked out. bondo up the holes you have now.,.

 

 

double curved spider II.jpg


Edited by Pinbout, 22 November 2017 - 10:45 AM.

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#16 SeaBee1

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Posted 22 November 2017 - 09:54 AM

First, welcome to CN!

 

If you are really into DIY, then an offset vane spider really is the way to go. Jeff said he would never use anything else, and I would have to echo that. I built mine around a design by Gary Wolanski, who, unfortunately no longer makes his spiders. Here is a pic of mine...

 

gallery_241784_6248_241459.png

 

^^^ A drill press and a hack saw is all you need. There is virtually zero flex and absolutely no vibration in this spider. It stays collimated unless I disassemble the scope, which I rarely do since it lives ready to go in my garage. And even then it is usually only a small tweak needed. A commercial spider from AstoSystems will certainly serve you well... but you built your own scope... in the spirit of DIY, wouldn't a new spider built by your own hand just add that little bit of extra satisfaction we all seek?

 

Best regards!

 

CB



#17 NeilPerlin

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Posted 22 November 2017 - 12:08 PM

its not wide enough, that's why its shakin'

 

you material choice should be fine if you remake it like below...

 

just shorten the screws after you get it worked out. bondo up the holes you have now.,.

 

 

attachicon.gifdouble curved spider II.jpg

Okay, so this is basically creating a 2-sided curved vane, or essentially a 4-vane.



#18 NeilPerlin

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Posted 22 November 2017 - 12:12 PM

First, welcome to CN!

 

If you are really into DIY, then an offset vane spider really is the way to go. Jeff said he would never use anything else, and I would have to echo that. I built mine around a design by Gary Wolanski, who, unfortunately no longer makes his spiders. Here is a pic of mine...

 

gallery_241784_6248_241459.png

 

^^^ A drill press and a hack saw is all you need. There is virtually zero flex and absolutely no vibration in this spider. It stays collimated unless I disassemble the scope, which I rarely do since it lives ready to go in my garage. And even then it is usually only a small tweak needed. A commercial spider from AstoSystems will certainly serve you well... but you built your own scope... in the spirit of DIY, wouldn't a new spider built by your own hand just add that little bit of extra satisfaction we all seek?

 

Best regards!

 

CB

Thanks. A pleasure to be here.

 

I've gotten some very good suggestions for DIY spiders. I think what I'm going to do is buy an Astrosystems spider and hub for the moment, just to get going with the 10". I have mapped out of number of other designs that I'd like to try, all either 6" or 8" to let me try these designs quickly, and I can see trying these various DIY designs for them.

 

And that will add a lot of satisfaction.

 

Regards,

Neil


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